I've seen tutorials on how to make a windows usb/flash boot drive on a mac using a windows iso & bootcamp. I've also seen tutorials on how to boot a mac from a usb drive (hold down alt when booting). However what I'm trying to do is to make a windows boot drive then boot my mac from it (installing all the 'stuff') and I'm getting stuck.

I have a late 2013/early 2014 Macbook Pro w/ 8GB RAM (but only 128GB of internal SSD) hence why I need to install windows on an external drive. I'm trying to install the latest version of the windows 10 insider preview (testing the waters of windows development).

Here's where I'm getting stuck:

I've seen a tutorial of this and apparently there's supposed to be a 4th drive partition called 'BOOTCAMP' which you then format.

What I've Been Doing:

I've connected my external SSD via USB and in the Bootcamp Assistant I checked the first 2 tasks. I select the SSD and let Bootcamp do it's thing. After it finished I restarted my mac while holding down the alt key. I get the option to choose between my HD ('Macintosh HD'), a drive called 'Windows' and a drive with a name beginning with 'e' (not sure - although it's just a higher-res version of the windows drive it seems).

Choosing windows, I follow the setup instructions until I get to the part shown in the photo, so obviously I'm doing something wrong (probably those pesky partitions).

Any help is appreciated.

EDIT: I wasn't able to install windows so it is bootable from an external drive but I was able to partition my internal drive with bootcamp after reinstalling OSX, then everything else worked as intended. I hope this helps others.

  • Your image is displaying the contents of your Macs internal drive. After holding down the alt key, you selected Windows. This is done only for BIOS/MBR windows installs, therefore you are correctly getting a message that the disk has a GPT partition style. You can not install Windows, for a BIOS boot, to a GPT partitioned disk. You must use BIOS boots for MBR partitioned disks and EFI boots for GPT partitioned disks. Confused? If not, you are not trying enough. – David Anderson May 7 '16 at 21:55
  • @DavidAnderson I guess I am trying enough 'cos I'm definitely confused :P - Would you suggest I do anything differently? EFI sounds like the third option, should I choose that one? When I tried it I got the same result though. I feel like before bootcamp begins, I should partition the external SSD but I'm not experienced enough in the area to be comfortable doing that (I know the partitioning is reversible though so I suppose I could give it a try). Thanks for answering, anyway :) – nanothread May 7 '16 at 22:09
  • I only know of two options: BIOS verses EFI boot methods. What is the third method? – David Anderson May 8 '16 at 1:00
  • Don't you need 'Windows ToGo' for an external boot drive to work? I didn't think regular Windows would boot from a removable... – Tetsujin May 8 '16 at 6:23
  • @DavidAnderson sorry for the confusion, I meant when I hold down alt while restarting I get to choose between my mac's HD, a drive call Windows, and a drive called efi-something. The last two seem to do the same thing, just at different resolutions (although choosing he Windows drive displays a message 'loading from bootcamp created drive' whereas the efi just loads right into Windows setup. – nanothread May 8 '16 at 6:42

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